Blackfyre — MG—01 · CrossInk sleep screens (Xteink X4 Pro, 480 × 800 portrait)

Custom (full screen): the six BMPs
  01-sigil-dark.bmp … 06-horizon.bmp   4-bit, four greys (05-truchet: 1-bit)
  Copy them into /.sleep/ on the SD card → Settings → Sleep Screen → Custom.
  The device picks one at random; for a fixed one, copy it to /sleep.bmp.

Page Overlay (transparent, drawn over the page you were reading): the four PNGs
  o1-sigil-dark.png … o4-signal.png    8-bit grey + alpha, fully transparent or opaque
  Copy them into /.sleep/ as well → Settings → Sleep Screen → Page Overlay.
  For a fixed one, copy it to /sleep.png. Custom mode ignores the PNGs, so both sets can share the folder.

Copy through File Transfer or USB Drive mode: the firmware indexes /.sleep/, and files added while it is off
may not be picked up until the index is rebuilt.